The absorption of fluoride in a variety of infant foods has been determined by measuring the amount of fluoride remaining in the upper segment of the gastrointestinal tract of large rats 6 hours after force feeding food containing a known amount of fluoride to animals starved for 16 hours. The "blank" for the model system consisting of residual fluoride in the upper gastrointestinal tract of starved animals and fluoride contributed by the diffusion cell and reagents was 0.147 +/- 0.0197 Mug. Mean values for the percent of the fluoride absorbed from infant foods thus far investigated ranged from 87.4 to 99.5%. Contrary to the results of other investigators the bioavailability of fluoride in low concentration from milk was found to be 96.5% using this model system. The bioavailability of fluoride from milk products and adult foods is also being investigated.